Optics Meeting April 12 2022 230PM ET

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Agenda

- Blocker studies (Kate) - Optics map update (Hanjie) [1]

- Background rate expectations at GEMS (David) [2]

- Photon Energy deposition in Argon Gas (Bill) [3]

- Updates on Reproducing Hanjie's Plots (Vassu) [4]

Attendance

Hanjie, Kate David, Ciprian, Bill, Zuhal, Brynna, Vassu

Minutes

• need a new Zoom Link for future meetings
• Kate is studying effect of changing Blocker from 100% W to 90% W/10% Cu (for manufacturing/engineering). No significant difference seen using beam generator (but this is mainly sensitive to the inner bore radius, which doesn't change). Will look at 12C generator events, which would be more sensitive to punch-through.
• Hanjie has made good progress with simplified (sparse) optics matrix. Results were from 3-pass 12C generator, using 16 Sieve holes (12 of which are at unique radii). Uses "exact" target variables (i.e. exact theta, p, phi, Z). Gets good reproduction theta_tgt using r and r', with small residuals. Next: need to rescale r' variable so that it has similar magnitude to r. Need to use "hole" coordinate to get theta-tgt. Discussed next steps for Vassu, Kate, Zuhal. Also discussed longer-term plan. Need to check that our method will allow is to reconstruct the correct kinematic factor. Need to start planning now how to do uncertainty analysis for kinematic factor, as we develop tools. Should look at correlations between target quantities, on the effect of imperfections in tracking data (r,r',phi,phi'), in knowledge of target foil z-location, in beam position, in collimator, etc. on kinematic factor.
• David sees that low-energy electrons and gamma and x-rays should not produce a problem with singles in the GEMs based on the high stats "high precision" GEANT 4 simulations. This results show no x-rays below 50 keV or so However, Cip has found documentation for a different physics list for GEANT that is better for very low-energy electromagnetic processes. We should try that. Bill shows that the worry is that below 50 keV the photoelectric effect cross section in Ar (or Cu) rises rapidly, so if there is a copious flux of these x-rays, there could be high singles rates in the GEMs. Stony Brook has a 0 - 50 KeV x-ray generator, with peak flux around 8 keV, one could use this to test x-ray detection efficiency with prototype GEM. We should run simulation with the low-energy EM physics list to get the spectrum of < 50 KeV x-rays.
• Vassu working on reproducing Hanjie's earlier results. Results look good. Leakage from the edge of the sieve is observed. Since the engineers tell us they prefer a sieve made from a complete annulus, as opposed to the 7-fold "peta;" design, we should probably move to that in simulation - would avoid edge effect "leakage".

Meeting link information

Meeting ID 970 3027 1000

Meeting URL

https://umass-amherst.zoom.us/j/97030271000

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